QUANTUM MOLECULAR MODELLING OF DIFFUSION PROCESS DURING PHASE CHANGE IN AMORPHOUS CARBON
( Pp. 13-18)

This paper purpose simulation performing to explain processes taking place in phase-change memory creation. Ab initio quantum simulation of atomic diffusion in amorphous carbon during phase change process is presented. It is shown that thermal effects lead to creation of a graphitic layers structure in a molecular system. Calculations show that in conditions of thermally induced phase change the diffusion process is anisotropic and forced by the fusion of atoms with different bonds and creation of covalent bonds. Time depended process of increasing mean square displacement differs from Einstein relation due to atoms interaction and formation of covalent bonds. Such a structure corresponds to increasing of electric conductivity in comparison with amorphous structure. The density of charge carriers is increased in the area of graphitic surfaces. Obtained dependencies help to understand the mechanism of phase change in experiments directed to the making of phase change memory on the base of amorphous carbon [1]. IBM Blue Gene/P supercomputer installed at the Faculty of Computational Mathematics and Cybernetics of the Moscow State University is used for calculations

Popov A.M., Shumkin G.N., Nikishin N.G., (2014), QUANTUM MOLECULAR MODELLING OF DIFFUSION PROCESS DURING PHASE CHANGE IN AMORPHOUS CARBON. Computational Nanotechnology, 2 => 13-18.

Sebastian A., Pauza A., Rossel C., et al. Resistance switching at the nanometre scale in amorphous carbon // New Journal of Physycs. 2011. Vol. 13. P. 013020.
Rueckers T., Kim K., Joselevich E., et al. Carbon nanotube based nonvolatile random access memory for molecular computing // Science. Vol. 289(5476). P. 94-97.
Meijer G. Who wins the nonvolatile memory race // Science. 2008. Vol. 319(5870). P. 1625-1626.
Wuttig M., Yamada N. Phase-change materials for rewritable data storage // Nat. Mater. 2007. Vol. 6(12). P. 1004.
Standley B., Bao W., Zhang H., et al. Graphene-based atomic-scale switches // Nano Lett. 2008. Vol. 8(10). P. 3345-3349.
Robertson J. Diamond-like amorphous carbon // Materials Science and Engineering: R: Reports. 2002. Vol. 37(4-6). P. 129-281.
Silva R. Properties of amorphous carbon. The Institution of Engineering and Technology, 2003.
Takai K., Oga M., Sato H., et. al. Structure and electronic properties of a nongraphitic disorded carbon system and its heat-treatment effects // Phys. Rev. B. 2003. Vol. 67(21). P. 214202-214212.
Ronning C., Griesmeier U., Gross M., et al. Conduction processes in boron- and nitrogen-doped diamond-like carbon films prepared by mass-separated ion beam deposition // Diamond and Related Materials. 1995. Vol. 4(5-6). P. 666-672.
Jornada F. H., Gava V., Martinotto A. L., et al. Modeling of amorphous carbon structures with arbitrary structural constraints // Journal of Physics: Condensed Matter. 2010. Vol. 22(39). P. 395402.
He Y., Zhang J., Guan X., et. al. Molecular Dynamics Study of the Switching Mechanism of Carbon-Based Resistive Memory // IEEE Transactions on Electron Devices. 2010. Vol. 57(12). P. 3434-3441.
Shumkin G.N., Zipoli F., Popov A.M., Curioni A. Multiscale quantum simulation of resistance switching in amorphous carbon // Procedia Computer Science. 2012. Vol. 9. P. 641-650.
SHumkin G.N., Popov A.M. Modelirovanie iz pervykh printsipov fazovogo perekhoda v amorfnom uglerode // Matematicheskoe modelirovanie. 2012. T. 24, N 10. S. 65-79.
Popov A.M., Nikishin N.G., SHumkin G.N., Mnogomasshtabnoe kvantovoe modelirovanie protsessa strukturnogo fazovogo perekhoda i teplovogo proboya v nanotochke amorfnogo ugleroda // Computational nanotechnology. 2014. N 1. S. 17-25.
Marx D., Hutter J. Ab initio molecular dynamics: Theory and implementation // Modern Methods and Algorithms of Quantum Chemistry. John von Neumann Institute for Computing, Forschungszentrum J lich, 2000. P. 329-477.
Andreoni W., Curioni A. New Advances in Chemistry and Materials Science with CPMD and Parallel Computing // Parallel Computing. 2000. Vol. 26(7-8). P. 819-842.
Kohn W. Density Functional and Density Matrix Method Scaling Linearly with the Number of Atoms // Phys.Rev.Lett.1996. Vol. 76(17). P. 3168-3171

multiscale quantum-mechanical molecular dynamics codes, phase transition in amorphous carbon, the memory on the phase transitions, nanotechnology, the supercomputer IBM Blue Gene/P.